Induced resonance makes light sterile neutrino Dark Matter cool

Understand

We describe two new generation mechanisms for Dark Matter composed of sterile neutrinos with ${\cal O}(1)$ keV mass.

• The model contains a light scalar field which coherently oscillates in the early Universe and modulates the Majorana mass of the sterile neutrino.
• In a region of model parameter space, the oscillations between active and sterile neutrinos are resonantly enhanced.
• This mechanism allows us to produce sterile neutrino DM with small mixing angle with active neutrinos, thus evading the X-ray constraints.